Different texture space in the same mesh?
Unless I'm mistaken, the texture space is an attribute of the texture, not the material, so if you have two materials with different textures, each texture will have its own texture space; if you have two materials that use the same texture, both materials will have the same texture space. So, you can have two different texture spaces, but they need to be assigned to different materials, although the two materials themselves can be identical (except for the material name), one for each texture.